As shown in FIG. 36 which is a partially simplified cross-sectional view, a prior art combination weighing machine includes a cone-shaped distributing table 1 onto which articles 2 to be weighed are supplied. The distributing table 1 distributes the articles 2 outward of the outer periphery of the table 1 by centrifugal force, for example. The articles 2 moved outward of the periphery of the distributing table 1 are fed to a plurality of straight feeders 3 disposed along the outer periphery of the distributing table 1. The straight feeders 3 transport the articles 2 successively outward. The articles 2 discharged from a distal end of each straight feeder 3 drop into a supply hopper 4 disposed beneath the distal end of the feeder 3. The articles 2 in the hoppers 4 are then fed to weighing hoppers 5 which are disposed beneath respective ones of the supply hoppers 4. The articles in each weighing hopper 5 are then weighed by a weight detector 6 which supports that weighing hopper 5. After the articles 2 are weighed, a gate 7 inside each weighing hopper 5 is opened and the weighed articles are fed to a memory hopper 8 disposed beneath the weighing hopper 5. When the weighing hoppers 5 are emptied, other articles are supplied to the weighing hoppers 5 in a manner similar to the one described above. The measured weights of weighed articles in the respective weighing hoppers 5 and the measured weights of weighed articles in the respective memory hoppers 8 are arithmetically combined and processed, and the combination of measured weights which is equal or nearest in weight to a predetermined weight is selected. The articles corresponding to the selected weight are discharged from the weighing hopper 5 and the memory hopper 8. The discharged article 2 are fed to a collection hopper 11 via an individual chute 9 and a collecting chute 10, where they are fed to a packaging machine 12.
Usually, the prior art combination weighing machine shown in FIG. 36 requires at least ten to fourteen weighing hoppers 5, although the number depends on a required measuring precision. These ten to fourteen weighing hoppers 5 are disposed beneath the distal ends of the respective ones of ten to fourteen straight feeders 3. Then, the diameter D (see FIG. 36) of a circle on which the weighing hoppers 5 are disposed is relatively large. For feeding articles selected for combination to the packaging machine 12, the selected articles must be gathered to one location above the packaging machine 12. Therefore the selected articles are fed to the single collection hopper 11. Accordingly, the diameter D of the prior art combination weighing machine is relatively large as shown in FIG. 36, and the length R of the path from the respective weighing hoppers 5 to the collection hopper 11, too, is long accordingly.
For weighing articles which are sticky or adhesive, if the length R of the path 13 is long, amounts of articles sticking to inside walls of the individual chutes 9 and collecting chute 10 which together form the path 13 increase, which results in lowering of the weighing precision of the combination weighing machine.
With the combination machine shown in FIG. 36, the use of the memory hoppers 8 increases the number of weighed articles which can be combined, which can improve the combination weighing precision. However, with this machine, because weighed articles 2 in the weighing hoppers 5 must be removed into the memory hoppers 8, a larger amount of articles, when they are sticky or adhesive, will adhere to the weighing hoppers 5 and the memory hoppers 8, which degrade the combination weighing precision. Then, for sticky or adhesive articles, it sometimes become impossible to use the memory hoppers 8 in order to maintain a desired weighing precision.
In order to maintain a desired weighing precision without using the memory hoppers 8, the number of the weighing hoppers 5 may be increased. However, with an increased number of weighing hoppers 5, the diameter D shown in FIG. 36 increases and, accordingly, the length R of the path 13 also increases. Therefore there is a limitation on the number of the weighing hoppers 5 which can be increased. Furthermore, the use of a larger number of weighing hoppers 5 undesirably increases not only the cost but also the size of the weighing machine.
In the combination weighing machine shown in FIG. 36, articles in one weighing hopper 5 or articles in one memory hopper 8 beneath the weighing hopper 5 are selected for combination, the articles in the weighing hopper 5 are discharged and the weighing hopper 5 becomes empty. Then, another articles are fed to the empty weighing hopper 5 for weighing. Accordingly, as long as articles in a weighing hopper 5 or in a memory hopper 8 beneath that weighing hopper 5 are not selected for combination and, therefore, not discharged, the weighing by that weighing hopper 5 is interrupted and, therefore, no further articles can be weighed. There are always a plural number of such weighing hoppers 5 that discontinue weighing during the operation of the combination weighing machine. Thus, the efficiency of the plural weighing hoppers 5 as a whole is undesirably low.
Another problem in the combination weighing machine shown in FIG. 36 is that since articles selected for combination are discharged from the weighing hoppers 5 or the memory hoppers 8 and transported along the inner walls of the individual chutes 9 and the inner walls of the collecting chute 10 to the packaging machine 12, it will take a relatively long time for the articles, in particular, sticky or adhesive articles to move along the path 13, and, hence, it will take a long time for the weighed articles to be packaged in the packaging machine 12.
One object of the present invention is to provide a combination weighing machine which can combination-weigh adhesive or sticky articles with an improved weighing precision, which can provide improved operating efficiency for weighing hoppers, and which has improved weighing speed. Another object is to provide a compact combination weighing machine which has a relatively small size.